Field of the Invention
This invention relates to a post-processing apparatus with a detector for detecting a solution's temperature, by which a photosensitive layer in a non-image area of an organic photoconductive master plate that has been prepared on a platemaker through the steps of exposure, development and fixing is washed off to prepare a master plate having an image of printing quality formed thereon.
When preparing masters with image of printing quality formed by means of conventional platemakers, a sheet of zinc oxide master (hereinafter abbreviated as "ZnO master") or an organic photoconductive master plate using an aluminum substrate (hereinafter abbreviated as "OPC master plate") is selected depending upon various conditions such as the mode of printing, the number of prints and the method of paper feed; after charging for each master, the master is transported to an exposure stage where a latent image of the original is formed; then, the master is sent to a delivery transport unit where the original image is rendered visible (developed) and fixed before it emerges on a delivery tray.
In the case of a ZnO master, the one which has just been processed on the platemaker is sent as such to a printing machine. However, in the case of an OPC master plate using an aluminum substrate, the processed plate is transported to a post-processing apparatus where the photosensitive layer in the non-image area of the master is washed off by spraying a processing solution controlled at an appropriate temperature, thus yielding a master plate on which a desired image of printing quality has been formed. Since the processing solution for washing off the photosensitive layer in the non-image area requires very strict temperature control, the master plate just processed on the platemaker is first sent to the post-processing apparatus where the spray of a temperature-controlled processing solution is applied to the photosensitive layer in the non-image area, so that it becomes sufficiently swollen and wet to be stripped and washed off.
The conventional post-processing apparatus for OPC master plates has only a temperature sensing device submerged in the tank of processing solution. If the tank has a large capacity, a temperature variation occurs to the processing solution depending on the specific site of measurement, thereby making it extremely difficult to ensure that the temperature of the processing solution is strictly held closely at constant level throughout the interior of the tank. As a consequence, temperature fluctuations occur while the processing solution is sprayed and the resulting failure to achieve positive stripping and washing-off of the photosensitive layer in the non-image area has made it impossible to prepare a master plate on which an image of good quality has been formed.